Proverbs 21:4

This may be taken as showing us, 1. The marks of a wicked man. He that has a high look and a proud heart, that carries himself insolently and scornfully towards both God and man, and that is always ploughing and plotting, designing and devising some mischief or other, is indeed a wicked man. The light of the wicked is sin. Sin is the pride, the ambition, the glory and joy, and the business of wicked men. 2. The miseries of wicked man. His raised expectations, his high designs, and most elaborate contrivances and projects, are sin to him; he contracts guilt in them and so prepares trouble for himself. The very business of all wicked men, as well as their pleasure, is nothing but sin; so Bishop Patrick. They do all to serve their lusts, and have no regard to the glory of God in it, and therefore their ploughing is sin, and no marvel when their sacrificing is so, Pro 15:8.

— Matthew Henry's Concise Commentary (public domain)

high look--(Compare Margin; Psa 131:1). proud heart--or, "heart of breadth," one that is swollen (compare Psa 101:5). ploughing--better "lamp," a frequent figure for prosperity (Pro 20:20); hence joy or delight.

— Jamieson-Fausset-Brown Commentary (public domain)